/* eslint no-shadow: 0 */

const test = require("tap").test;
const ss = require("../dist/simple-statistics.js");

function rnd(x) {
    return Math.round(x * 1000) / 1000;
}

test("sample variance", function (t) {
    t.test("can get the sample variance of a six-sided die", function (t) {
        t.equal(rnd(ss.sampleVariance([1, 2, 3, 4, 5, 6])), 3.5);
        t.end();
    });

    // confirmed in R
    //
    // > var(1:10)
    // [1] 9.166667
    t.test("can get the sample variance of numbers 1-10", function (t) {
        t.equal(rnd(ss.sampleVariance([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])), 9.167);
        t.end();
    });

    t.test(
        "the sample variance of two numbers that are the same is 0",
        function (t) {
            t.equal(rnd(ss.sampleVariance([1, 1])), 0);
            t.end();
        }
    );

    t.throws(function () {
        ss.sampleVariance([1]);
    }, "the sample variance of one number cannot be calculated");

    t.throws(function () {
        ss.sampleVariance([]);
    }, "the sample variance of no numbers cannot be calculated");

    t.end();
});
